a) Field of the Invention
This invention relates generally to photographic image-modifying equipment, and more particularly, to photographic image-modifiers for introducing optically generated grain-effects to a photographic negative during its exposure of an image.
b) Description of Related Art
The art of creating special effects in the field of photography has been very active in the past and continues to grow with the increasing interest in photography and the desire for more interesting visual illusions. Devices have been developed, for example, to alter an image prior to or during its exposure on film. Typically, these devices are attached at the end of the lens of a camera, and directly interfere with the light prior to it reaching the film. The alterations of effects applied to the incoming light vary from common color-filtering changes to superimposing "sub-images" onto the same frame of film that is recording the "real" image. For example placing an opaque, pre-shaped matte in front of a portion of the incoming light will block a correspondingly shaped portion of the film. This results in an unexposed area of film which may be later "filled-in" with another image to create one desired illusion or effect. Similar diffusion mattes are used in "still photography" to produce progressively under-exposed boarders to a frame of film being exposed, creating a vignette boarder.
Conventional devices have also been used to superimpose an image of characters such as a date or other alpha-numeric information onto a portion of an image on a frame of film. Typically, these devices, such as the device disclosed in U.S. Pat. No. 1,504,959 issued to Leschbrandt, include a translucent plate (or ribbon) having, for example, opaque characters positioned at the film plane in a camera. The plate of characters is aligned adjacent to and in front of the surface of the film. Light from an external source or light generated from within the camera is used to superimpose selected characters of the plate onto a portion of the film.
U.S. Pat. No. 3,916,423, issued to Ueda et al. discloses a device for transposing information (characters, lines or designs) onto the surface of film during exposure of the film to an image. A transparent plate having an opaque mask is attached to a film cartridge in front of and adjacent to a frame of film. During exposure, a portion of the light from the image is blocked by the opaque mask located on the transparent plate prior to the light reaching and exposing the film. The result is under-exposed regions of the film (negative) corresponding to the particular shape of the opaque mask. When the negative is used to expose a positive print, the shape of the particular opaque mask will be positively transposed in the form of dark overexposed regions in the final print.
One limitation with these prior art special effects devices is that they all rely on blocking a portion of the incoming light prior to the light reaching the film. Although many effects may be created using the prior art methods employing opaque masks, many other effects require more subtle, diffusion methods.
Oftentimes, when a photograph is taken of a particular subject within a particular scene, the lighting conditions and lighting distribution within the scene and the reflective characteristics of the subject will cause areas on the film negative to become either overexposed or underexposed relative to the "normal" exposure range of the film. A conventional camera usually includes at least one integral light meter which is used to measure the average intensity of light entering the camera prior to exposing the film. The light meter generates an electrical signal that is interpreted by a computer and is used to control either the size of the aperture of the lens, the speed of the shutter, or both, so that the average intensity of light is compensated throughout the entire picture, as recorded by the film. With some more advanced cameras, such as the N-90, N90s, and F5 cameras manufactured by Nikon of Japan, several separate light meters are used, each measuring the intensity of light within a particular zone or region of the frame (an upper region is used to measure the intensity of light from the sky of the scene, for example. Although the use of several light meters to measure the different light intensities at different regions of a framed scene provides a more accurate average light intensity reading, the camera cannot control the amount of light from a particular region of the framed scene reaching the corresponding region of the film without effecting the amount of light reaching the other regions of the film. In other words, the overall density of the negative can be corrected by adjusting either the aperture of the lens or the operating speed of the shutter, however, this exposure correction has a uniform effect over the entire recording area of the film (i.e., the frame). If the aperture is decreased to lessen the amount of light reaching the film to compensate for the "bright" spots of the subject or scene, for example, the otherwise "neutral" or normal areas of the subject or scene will now become too dark. If the speed of the shutter is prolonged to "burn in" the darker regions of the image, the normal areas will become unacceptably overexposed and appear "washed out".
Unfortunately, since a conventional camera merely measures the average of the total received light entering the camera of a particular image, many pictures end up with a portion of the recorded image either overexposed (to dark) or underexposed (washed out).
In an attempt to prevent this relatively common exposure malady from ruining an otherwise good picture, serious photographers have made it common practice to take several pictures of the same image (i.e., bracket the image) and then vary the exposure of the image between each shot, (typically around 1/3 EV) so that each image offers a slightly different exposure from which the photographer may later select the recorded image that averages the received light most accurately. The above-identified N-90 manufactured by Nikon offers a bracketing feature with its M-26 data-back accessory which allows the camera to automatically take a selected number of pictures and vary the exposure a preset degree between shots.
There are several problems with the bracketing technique of photography. Not only is a lot of film exposed for few different images, only relatively expensive cameras offer exposure control, let alone automatic bracketing of the exposure. Also, although exposure bracketing provides several pictures to select from, since the camera's exposure meter must account for the total received light and may not locally correct the exposure of a portion of the image frame, all of the bracketed pictures will show varying degrees of over and under-exposure. In other words, if there is an overexposed region of an image, bracketing will not correct the exposure of that particular region, merely hide it by changing the total exposure throughout the image, as recorded by film.
Other attempts have been made to control the exposure of a particular region of a frame of film, without effecting the exposure of the other regions of the frame of film. Special segmented, or zone filters include regions of varying opacity which may be aligned within a particular scene to compensate for highlighted regions, such as a cloudy sky. These filters rarely align with the image detail and are only useful when the specific regions defined by the filter align with the regions of the scene.
Once a negative is developed, any underexposed or overexposed regions may be compensated during the production of a photographic print using well known techniques known as "dodging" or "burning" in which a density mask (made from opaque and semi-transparent sheet material) is held in the exposure path (over the photographic paper) when a print is being made from a negative. The mask is used to selectively protect overexposed areas of the negative from a portion of the light projected to the photographic paper during image enlargement (or print processing). However, these techniques are used in expensive custom print processing, not in cheaper automated print processing. These techniques are difficult to uniformly perform on a repeated basis because of the inherent inaccuracies in placing the density mask in the proper location each time a print is made and also require a great amount of time to adjust the mask from print to print. Furthermore, the results of these exposure compensating techniques are not known until after the print is exposed and developed. If the results are unsatisfactory, another attempt must be made in a trial-and-error method until a satisfactory print is produced.
Although the art of photography is always open to creative input, as a general rule, good image quality of photographs tends to include some consistent characteristics. Among these involve sharpness, tonal depth, and graininess, which are each somewhat related. Using conventional film (and assuming an image has been recorded in focus on the film), sharpness tends to be directly related to the film's ISO speed wherein the lower the film's ISO speed, such as 25 ISO, the finer the grain and the sharper the image (i.e., the image will be recorded by the film at a higher resolution because the grain of the emulsion is finer). High speed films, such as 1600 ISO have a tendency to record an image with high grain characteristics, resulting in a somewhat blurred image revealing "soft" detail.
The term "grain" in photography is used to describe the granular texture that appears, to some degree, in all processed photographic materials. In black and white photography, the grains are minute particles of black metallic silver which constitute the dark areas of a photograph. In color photography, although the metallic silver is chemically removed during processing, extremely fine blotches of dye remain on the film and retain the appearance of "grain".
The emulsion grain of film may be considered analogous to the pixel resolution of a television set. The finer the resolution of the television screen, the finer the "grain", and the sharper an image will appear on the screen. Similarly, should the resolution (or number of pixels per inch) be reduced (and thereby increased in size), the more noticeable each pixel (or grain) will be, and therefore, the less sharp the image will appear. Since each grain, (or pixel in a TV set) translates a single representative tonal shade of the gray scale, the finer the grain, the higher the "sampling" rate over a given area of an image and the more accurate the tonal depth or tonal transition (transition from white to black regions of the image) will be recorded on the film.
Since emulsion grain tends to "dull" an image by lowering the recorded resolution of the film, this film characteristic is generally considered undesirable and much research and development has been directed to eliminating (or at least minimizing) the effects of grain from any processed photograph, either at the transparency or negative stage, or in the final print. Graininess is also generally undesirable by photographers because by achieving high grain in a negative, the tonal depth of the image is adversely effected, as described above. Coarse (or high) grain within a negative or picture tends to digitize an image so that each "grain" (or pixel) or in some cases, each grain cluster (a group of grains within the emulsion of the film) translates a real image having a gradation of tones including several shades of gray (at a particular region of the image) into a single shade of gray on the film. This digitizing of the tonal information of the image tends to create a dull, choppy, high-contrast, recorded image having little tonal depth or realism.
As discussed above, graininess of film is generally a factor of film speed, however, a low-speed film (100 ISO) which should normally result in a fine grain representation of an image, may be "pushed" during processing of the film so that the film is developed as if it were a higher speed film, such as 400 ISO film. In such instance, the emulsion grain may appear coarser than normal. Similarly, higher speed film may be "pulled" during processing so that it is processed as if it were a lower-speed film. In doing so, grain size and grain effect may be altered.
Although emulsion grain is typically associated with poor image quality, as discussed above, it can be used beneficially to create a certain mystique and/or softness of a subject that is otherwise difficult to obtain, using, for example, conventional soft-filter techniques known in the art. It is known, for example, to introduce a grain effect during the enlargement process wherein an image of a normal negative is enlarged (or at least transposed) onto photographic paper. As is known by those skilled in the art, a negative is positioned within and held by a negative carrier. The negative carrier is then positioned within an enlarger so that light may pass through the held negative and its exposed image projected onto a sheet of photographic paper. To create a grain-like effect during the enlargement process, a potato starch may be applied to a glass plate located adjacent to the negative within the negative carrier. The potato starch layer creates a "stochastic screen" which comprises millions of "grain-like" structures of the transparent potato starch. This procedure is described in U.S. Pat. No. 822,532 to Auguste and Louis Lumiere, issued Jun. 5, 1906, and the process is currently used by LTI Labs of New York, N.Y. Although this process creates a grain-like structure on photographic paper simultaneously with the exposure of the image of the negative, the resulting grain is not effectively controllable and will vary in size and texture depending on the size of enlargement being made, the larger the print, the larger the grain. Also, this process of using potato starch to introduce a grain-like characteristic to a photographic print is considered custom photographic work and is inherently expensive to implement, by only select professional photographic labs.
Applicant has recognized the value of selectively introducing grain effects in a controlled manner to an image without effecting other characteristics of the photograph, such as tonal depth and sharpness.
It is accordingly an object of the invention to provide optically-generated grain effects to film without adversely effecting other characteristics of the film.
It is another object of the invention to provide a special effects device for use in photography which overcomes the limitations of the prior art.
It is another object of the invention to provide such a device which enables a photographer to transform photographic images into images having characteristics inherent in paintings of such images.
It is another object of the invention to provide such a device which enables a photographer to superimpose a translucent mask including random crackling onto an image, resulting in a final print which includes the craquelure characteristics of aged oil paintings.
It is another object of the invention to provide such a device which enables a photographer to superimpose a translucent mask onto an image to transpose the image to one having characteristics inherent in a water color painting.
It is another object of the invention to provide such a device which enables a photographer to superimpose a translucent mask onto an image to transpose the image to one having characteristics inherent in an oil pallet-knife type painting.
It is another object of the invention to provide a method and apparatus for producing a photographic negative wherein areas of overexposure and underexposure may be corrected prior to the film being exposed.
It is another object of the invention to provide a regional exposure correction to selected regions of an image to be recorded on film, wherein the regions may follow the specific contours of a scene, object or subject located within the image.
It is another object of the invention to provide a preview image of an exposure-corrected image prior to the image being recorded on film.
It is yet another object of the invention to provide various degrees of regional exposure correction to an image.
It is yet another object of the invention to provide a method and apparatus for selectively modifying an image using a single modifier located adjacent to the film.
It is yet another object of the invention to provide movement of a selected modifier during exposure so that a multitude of effects can be generated from a single modifier.